Ever make something just to see if you could? Yeah, we thought so. [serverframework] wanted to see if he could clone the remote that opens his neighborhood gate, inspired by the long distance ding-dong-ditch efforts of [Samy Kamkar].
This clone uses an ATtiny85 and an RF module to emulate and send the frequency that the gate is waiting for. To accomplish that, [serverframework] had to figure out both the operating frequency and the timing used by the remote. The crystal inside seemed to indicate 295 MHz, and a quick check of the device’s FCC registration confirmed it. Then he used an SDR dongle to watch the data coming across when he pressed the button, and ran it through Audacity to figure out the timing.
Unfortunately, the 295 MHz crystal is a rare beast, so [serverframework] had to transplant the original to the donor RF module. Then it was just a matter of programming the ATtiny85 to send the frequency with the right timing. It actually does a better job since the original has no timing crystal, and the ‘tiny is clocked with a standard 16 kHz oscillator. The code is available within [serverframework]’s excellent write-up, and you can see a tiny demo after the break.
There’s more than one way to clone a gate remote. This one leverages MQTT to turn friends’ phones into remotes.
Wouldn’t it be a 16 MHz crystal rather than 16 KHz ?
2 mistakes in 1 sentence.
>the ‘tiny is clocked with a standard 16 kHz oscillator.
16MHz? 16kHz isn’t too useful. It is a crystal, not oscillator.
os·cil·la·tor
/ˈäsəˌlādər/
noun: oscillator; plural noun: oscillators
a device for generating oscillatory electric currents or voltages by nonmechanical means.
If the crystal is being used to generate an oscillatory electric current or voltage by nonmechanical means, then it is a type of oscillator.
A crystal on its own doesn’t generate an electric current, oscillatory or otherwise. That job is the province of an oscillator combined with a suitable power supply. Such an oscillator may or may not employ a crystal as its primary resonant element.
Also, a crystal is arguably a mechanical device, as its mode of operation lies in the realm of acoustics and it is considered to be an electromechanical component. Therefore, the definition of ‘oscillator’ which you supplied is at least debatable, if not outright erroneous.
Correction: A crystal on its own doesn’t NORMALLY generate an electric current, oscillatory or otherwise. In the presence of sufficient vibration, or pressure applied directly to the quartz element, it can generate a voltage. This voltage will cause an electric current to flow if there is a path for the current between the terminals of the crystal.
He didn’t replace a ‘crystal’, but rather a SAW resonator.
No need to reverse engineer these they were well documented a long time ago and are not secure in any way…. You could have just bought a replacement remote for about 10 bucks and then it would still fit on your keychain…..????? Guess it depends on what your time is worth.
The article starts with “Ever make something just to see if you could?”
“Guess it depends on what your time is worth”
Some people prefer making something, figuring stuff out on their own and learning all sorts of technical skills in the process. I personally consider this time spend usefull.
While others hang around in bars, talking about football and politics or go to cinema’s and watch movies (and some watch youtube videos). As a technician, I doubt that this is a useful way of spending your time.
So regarding this project, useful or not, I’m sure that the person who done it learned lot’s and most likely had lot’s of fun doing it. In the end the mission was succesful, so what’s the problem?
Given that there are numerous projects like this already documented I didn’t think it was necessary to “figure out”… Given that the architecture is obsolete and abandoned in anything considered remotely secure, I do not recognize any value in doing it again. Given the use of off-the-shelf components, I don’t see anything relevant that was “learned”, i.e. designing and creating an RF (which in itself is very rudimentary, but would provide some experience and knowledge that is actually useful and relevant)…. It’s appears to be very common for people to make these mimic projects and then dub themselves “hackers”, which is a bit confusing. Is there a misunderstanding of what “hacking” means here? This is published under “microcontrollers, hacks” but you are not a “hacker” if you are doing something that has been done a thousand times over. You are a mimic. Just saying.
If this site were called “MimicADay” I wouldn’t be pointing these things out. I’m still looking for the “hacks”.
@nato You’re comments show your perspective and contain some assumptions about the motivatoins behind this project. I think I may have another perspective for you. Don’t you think this person may have just thought they would rather learn by doing? ie. Seeing if the tools they chose were up too the task? How is what they did “mimicking” anything if they didn’t use the existing documentation?
It seems to me that they had no hard deadline on this task and therefore could take the time to learn a new skill from scratch, by doing, just because they can.
Sure, if you have to make sure it is 100% accurate and completed quickly then look up existing versions of this and use one of them. I personally learn less doing it that way. I certainly don’t feel like I know the ins and outs of why and how it worked when I blindly mimic someone else’s work.
I just thought I would share this thought with you. Its how i chose to operate sometimes. I feel like I learn more that way. I also have a greater sense of accomplishment when something works if I did it from scratch.
There are plenty of other far more useless things on the internet you could spend your life criticizing in comments sections. Please seek those out and let the rest of us learn.
Yah, but he’s got to shut down ppl getting their hands dirty to validate his complaint on another post that new grads have no practical experience or enthusiasm for the topic.
RW, you are lacking in basic logic. I am poking at the site deciding to write this up as a “hack”, not at the person who was curious about RKE transmitters.
Breaking the original disappoints me. But I’m curious about “better”….does that mean on a very cold or very hot day, the original would be rejected as out-of-spec? If the protocol has enough slop to accept it, or the receiver’s timing follows the same temperature curve, then I don’t figure it’s actually better. There is only do or do not.
Nice. I wish someone would make one of these for ceiling fan remotes. Would be nice to make it work with alexa/SmartThings, etc.
I did something similar to this project with my adjustable bed. Luckily for me, it used a transceiver that is easily found on ebay. A little bit of work to figure out the commands, and now I can use Alexa/SmartThings to control the bed. No need to find the remote that fell down somewhere.
I’m super curious on this project with the adjustable bed. I’ve been trying for years to do something similar with mine but no luck from the mfg.
In case someone else wants to play with this and doesn’t have a donor, the SiTime SiT9122, at least, offers a programmable oscillator that can run at that range. I use their stuff at work. It’s really expensive but for a prototype, when you’re not yet sure exactly what frequency you need, or you need to match another frequency, it’s invaluable.
I wanted to do something similar with the cc1101 module, supposedly it’s a transciever that can run in the 300mhz range but haven’t had much luck.
There’s even some nice libraries for it.
36.864Mhz and 18.432Mhz crystals are not too difficult to source.
Multiply that by 8 (or 16) and you get 294.912Mhz. (Some cheap FPGA/CPLD’s PLL might do the trick)
It should be within margins (99.9701%) considering it’s only an AM receiver and I doubt garage openers use the best quality frequency filters in their radios.
( Anyone wants to figure out how fast you’d have to run toward the receiver to match 295Mhz with the doppler effect? )
You can also buy a slightly higher clock standard crystal and tune it down but that’s only practical for very-desperate one-off builds.
HAD article: https://hackaday.com/2010/05/10/hack-your-crystals-frequency/